ARROW-14931: [Python] csv/orc format strings missing from some datase…

…t docs

Closes #11814 from westonpace/bugfix/ARROW-14931--format-str-in-python-dataset-docs

Authored-by: Weston Pace <weston.pace@gmail.com>
Signed-off-by: Weston Pace <weston.pace@gmail.com>

python/pyarrow/dataset.py

@@ -568,8 +568,8 @@ def dataset(source, schema=None, format=None, filesystem=None,
         Optionally provide the Schema for the Dataset, in which case it will
         not be inferred from the source.
     format : FileFormat or str
-        Currently "parquet" and "ipc"/"arrow"/"feather" are supported. For
-        Feather, only version 2 files are supported.
+        Currently "parquet", "ipc"/"arrow"/"feather", "csv", and "orc" are
+        supported. For Feather, only version 2 files are supported.
     filesystem : FileSystem or URI string, default None
         If a single path is given as source and filesystem is None, then the
         filesystem will be inferred from the path.
@@ -757,10 +757,10 @@ def write_dataset(data, base_dir, basename_template=None, format=None,
         "part-{i}." + format.default_extname
     format : FileFormat or str
         The format in which to write the dataset. Currently supported:
-        "parquet", "ipc"/"feather". If a FileSystemDataset is being written
-        and `format` is not specified, it defaults to the same format as the
-        specified FileSystemDataset. When writing a Table or RecordBatch, this
-        keyword is required.
+        "parquet", "ipc"/"arrow"/"feather", and "csv". If a FileSystemDataset
+        is being written and `format` is not specified, it defaults to the
+        same format as the specified FileSystemDataset. When writing a
+        Table or RecordBatch, this keyword is required.
     partitioning : Partitioning or list[str], optional
         The partitioning scheme specified with the ``partitioning()``
         function or a list of field names. When providing a list of